1. Field of the Invention
This invention relates to an image forming apparatus such as a copying apparatus, a printer or a facsimile apparatus, and particularly to the technique of making a plurality of conveyance paths capable of being selected in conformity with the disposed state of a separable image reading portion.
2. Related Background Art
As a conventional image forming apparatus, the construction of an ordinary copying apparatus is shown in FIG. 8 of the accompanying drawings. In an image reading portion R, the image of an original placed on platen glass 1 is directed to a CCD 3 by an optical reading system 2 comprising an illuminating lamp, a reflecting mirror, and a lens and is converted into an electrical signal.
On the basis of this electrical signal, in an image forming portion P, a laser beam is applied to a photosensitive drum 4 uniformly charged by a primary charger 5, whereby an electrostatic latent image is formed. This electrostatic latent image is visualized into a toner image by a toner supplied from a developing device 6.
On the other hand, a sheet fed by sheet feeding means 7 has its skew feed corrected by its leading end striking against stopped registration rollers 8, and is sent to a transfer portion 9 by the registration rollers 8 being rotated so as to be synchronized with the toner image formed on the photosensitive drum 4.
In the transfer portion 9, the toner image on the photosensitive drum 4 is electrostatically attracted from the back of the sheet by a corona charger or the like, whereby the toner image is transferred onto the sheet.
The sheet onto which the toner image has been transferred has its electrostatic attractive force with respect to the photosensitive drum 4 removed by a separating charger 10, and thereafter is conveyed to a fixing portion 14 by a suction belt conveying portion 11.
The suction belt conveying portion 11 effects the conveyance of the sheet by a rubber belt 13 made of chloroprene while sucking the sheet by are drawn by a fan 12.
The sheet on which the toner image has been fixed by the fixing portion 14 is discharged onto a tray 16 outside the apparatus through a sheet discharging portion 15. Or the sheet is sent to a refeeding conveyance path 17 for both-surface copying or to a post-step such as sorting or stapling.
However, with the digitization of the image forming apparatus, there have been provided many products in which the image reading portion R (reader portion) and the image forming portion P (printer portion) can function as discrete members.
Between a case in which the image forming portion P is made to function as a printer and a case in which the image forming portion P is made to function as a copying apparatus, different processes are carried out in the sheet discharging process.
For example, when the image forming apparatus is used as a printer, a sheet processed as the head page is often discharged with its face down, and when the image forming apparatus is used as a copying apparatus, the sheet is often discharged with its face up, after which the sheets are subjected to a post-process such as stapling.
Which conveyance path is selected depends on a method whereby the installer (service engineer) of the image forming apparatus changes and installs a changeover member or the like in conformity with respective states.